Electrical relays



30, 1958 E. PADnlsoN 2,866,926

ELECTRICAL RELAYs Filed Aug. so, 1955 2 Smets-sheet 1 TIME Dec. 30,1958 v E. Fueunlmsm` 2,866,926

ELECTRICAL RELAYs FnedAug. so, 1955 2 sheets-sheet@ United States Patent F ELECTRICAL RELAYS Eric Paddison, Stadord, England, assigner to The English Electric Company Limited, London, England, a British company Application August 3l), 1955, Serial No. 531,361 Claims priority, application Great Britain October 1, 1954 Claims. (Cl. 317-167) This invention relates to electrical protective relays of the time-overeurrent type.

According to the invention, an operating electromagnet for an electrical time-overcurrent protective relay comprises a non-adjustable magnetic core having two core limbs positioned to dene a working airgap thereby to adapt the core to co-operate with a relay armature, said core having a body portion joining said core limbs and a llux leakage path adjacent the body portion and bridging said working airgap, a magnetizing winding having a unitary structure and loosely embracing said body portion of the core so as to be linked by a part of said iiux leakage path, and adjustable support means supporting the winding on said core and adapted to permit the adjustment of the electromagnetic coupling between the winding and the core by allowing the location of the winding with respect to the core and its llux leakage path to be adjusted.

According to a feature of the invention, said magnetizing winding has a larger internal cross-section than the external cross-section of the core body portion and said adjustable support means are adapted to permit an adjustment of the location of the Winding in a direction transverse to the main flux path in the core body portion.

According to another feature of the invention, said core is composed of fiat laminar stampings and said adjustable support means provide a positive location for said winding in a direction perpendicular to the planes of the stampings but allow an adjustment of the winding in a direction parallel with the planes of the stampings. The support means may comprise lugs rigidly attached to said winding at its ends and adjustable clamp means mounted on said core and adapted to clamp the lugs to the core.

According to an alternative feature of the invention, said winding has a smaller axial length than the part of the core which it embraces and said adjustable support means are adapted to permit an adjustment of the location of the winding in a direction aligned with the central axis of said part of the core.

In order that the invention may be well understood two embodiments of it will now be described with ref erence to the accompanying drawings in which:

Fig. l illustrates diagrammatically a magnetic core of a kind which is used in an induction disc type relay, there being on the core a coil Whose position is adjustable,

Fig. 2 shows a series of operating characteristics for a time-overcurrent relay embodying the core and coil arrangement shown in Fig. 1, the different curves corresponding to diierent positions of the coil relative to the core,

Fig. 3 shows a magnetic core and coil system according to the invention, the means for locating the coil with respect to the core being also shown,

Fig. 4 shows an alternative embodiment of the invention in which a magnetic core and coil system different from that shown in Fig. l are illustrated, and

2,866,926 Patented Dec. 30, 1958 ICG Fig. 5 shows the magnetic core and coil system of Fig. 4 with the coil in a different position relative to that shown in this latter figure.

A preferred embodiment of the invention will now be described with reference to Figs. 1, 2 and 3 of the accompanying drawings. The core is designed for use with an induction disc type relay, it being provided with a plurality of pairs of poles some of which may be fitted with shading means. The core section 4a is embraced by a magnetizing coil 5. The cross section of this coil 5 is made greater than that of the core section 4a. Thus, for example, the section 4a of the c'ore may be square whereas the cross section of the coil 5 may be rectangular and of such size that the coil may not be moved appreciably perpendicular to the plane of the core 4 but may be moved a substantial distance parallel to the plane of the core. In this Way the -coil 5 may be moved between two extreme positions one of which the coil occupies in Fig. l and the other of which is indicated by the broken outline 6.

In the position shown the coil 5 is linked by leakage flux which follows the path such as that shown, for example, by the arrow. This leakage ux which links the coil in this position is substantially greater than the leakage ux which the coil embraces in the other extreme position. Thus the relationship between the magnetizing current in the coil 5 and the magnetic effect produced in the poles of the core depends, to a small extent, upon the position of the coil 5 relative to the core section da.

In a time-overcurrent relay in which the torque applied to an induction disc by the magnetic core 4 depends upon the current in the coil S and the speed of operation of the relay depends upon this torque, it is usual for the relay characteristicto have a form such as that shown by the curves of Fig. 2. The greater the current the more rapid is the operation of the relay. The relay is made to have a particular operating characteristic and in the manufacture of many such relays it is desirable to have some means for adjusting the characteristic to allow for manufacturing variations and variations in the quality' of the magnetic core. It has been found that the movement of the coil 5, as shown in Fig. l, relative to the core section 4a, produces a variation in the operating characteristic of the relay which is sufficient, in many cases, to correct for manufacturing variations and enable the relay to be calibrated to cause its operating characteristic to conform with a standard scale. In Fig. 2 the curve A shows a typical characteristic which has been obtained with a relay in which the coil 5 is in the extreme position shown in Fig. l. Curve B shows the operating characteristic of the relay when the coil S is in the other extreme position, shown by the broken outline 6 in Fig. 1. The design of the relay may be such that the desired operating characteristic indicated by the broken line in Fig. 2 normally lies between the curves A and B appropriate to each relay. some position intermediate the two extreme positions enables the relay characteristic to be adjusted.

With reference to Fig'. 3, a means for locating the coil with respect to the core is shown. The coil 5 is fitted at each end with a projection 7. Each projection has a slot 7a arrangedperpendicular to the axis of the coil, and bolts 8, one at each end of the core section 4a, pass through the slots 7a and through the core 4. This enables the coil 5 to be adjusted between two positions corresponding to the bolts 8 being at the different ends of the slots 7o. Nuts 9 threaded on the bolts 8 may be tightened when the coil 5 is in a required position to hold the coil xed. An alternative embodiment of the invention will now be described with reference to Figs. 4 and 5 of the accompanying drawings.

In Fig. 4 a magnetic core and coil system is illustrated,

Thus, an adjustment of coil 5 toy The magnetic core 24is formed from stampings of sheet steel and is designed for use with an induction disc type relay. A feature of the core 24 by which it differs from they core 4 shown in Figs. 1 and 3 is that it is designed to have a strong leakage path adjacent one end tothe part of the core embraced by the coil system. In Fig. 4' this coil system is shown to be formed by a magnetizing coil 25, which embraces a core section 24a. The cross-section of this coil 25 is such that the coil -is a'close-sliding tit onthe core section 24a and the length of the coil. relative to the length of this core section is such that the coil may be adjusted relative to the core in the direction of the core section. The coil 25 may, therefore, be moved between two extreme positions. One of these positions is that shown in Fig. 4 and the other position is that shown in Fig. 5. In the position shown in Fig. 4 the coil 25 is linked by the strong leakage fluxwhich traverses an air gap 24b in the core 24. In the position shown in Fig. 5 an end of the coil 25 occupies this air gap 24b and the leakage tlux which traverses this air gap does not, therefore, link some end turns of the coil 25. Thus in moving from the position shown in Fig. 4 to that shown in Fig. 5 the coil 25 is moved from a position in which it fully embraces substantially the whole of the ilux traversing the core to a position in which it embraces only a part of this flux. This part will, of course, be the major part of the total liux but since only a slight adjustment of the flux linkage is normally required to adjust the operating characteristic of the relay there is a sufficient change in flux to achieve this object.

In Figs. 4 and 5 the leakage ux across the gap 24h is illustrated by the arrow.

The eiect which the coil adjustment has on the system shown in Figs. 4 and 5 is similar to that described with reference to Figs. 1, 2 and 3.

In order to tix the coil with respect to the core after the coil has been adjusted the coil 25 is fitted at each end with a projection 26. Each such projection has a slot 26a arranged parallel to the axis of the coil, and bolts 27 one at each end of the coil section 24a pass through slots 26a and through the core 24. Once the coil 25 has been adjusted, nuts 28 threaded on the bolts 27 may be tightened to hold the coil 25 tixed.

What I claim as my invention and desire to secure by Letters Patent is:

1. An operating electromagnet for an electrical timeovercurrent protective relay, comprising a non-adjustable magnetic corel having two core limbs positioned to define a Working air gap thereby to adapt the core tol co-operate with a relay armature, said core having a body portion joining said core limbs and a llux leakage path adjacent the body portion and bridging said working airgap, a magnetizing winding having a unitary structure and loosely embracing said body portion of the core so as to be linked by a part of said iiux leakage path, and adjustable support means supporting the winding on said core and adapted to permit the adjustment of the electromagnetic coupling between the winding and the core by allowing the location of the winding with respect to the core and its llux leakage path to be adjusted.

2. An electromagnet according to claim l, wherein said magnetizing winding has a larger internal cross-section than the external cross-section of the core body portion and said adjustable support means are adapted to permit an adjustment of the location of the winding in a direction transverse to the main ux path in the core bodyy portion.

3. An electromagnet according to claim 2, wherein said core is composed of at laminar stampings and said adjustable support means provide a positive location for said winding in a direction perpendicular to the planes of the stampings but allow an adjustment of the winding in a direction parallel with the planes of the stampings.

4. An electromagnet according to claim 2, wherein said support means comprise lugs rigidly attached to said windingr at its ends and adjustable clamp means mounted on said core and adapted to clamp the lugs to the core.

5. An electromagnet according to claim 1, wherein said winding has a smaller axial length than the part of the core which it embraces and said adjustable support means are adapted to permit an adjustment of the 1ocation of the winding in a direction aligned with the central axis of said part of the core.

References Cited in the tile ofthis patent UNITED STATES PATENTS 1,054,862 Paling a Mar. 4, 1913 2,085,549 Skeats June 29, 1937 2,376,730 Steinhotf May 22, 1945 FOREIGN PATENTS 230,540 Germany Jan. 31, 1911 474,781 Great Britain Nov. 8, 1937 612,100 Great Britain Nov. 8, 1948 617,706 Great Britain Feb. 10, 1949 

